Method of apportioning furnace-draft for batteries of steam-boilers



(No Model. y N. W. PRATT. I

METHODOE APPORTIO'NING FERN-AGE DRAFTTOR BATTERIE S 0 STEAM BOILERS. 1

Patented May 8, 18.88.

1 lllllll UNITED STATES PATE T OF ICE;

NAT. W. PRATLI, OF BROOKLYN, NEW YORK.

METHOD OF APPORTIONING FURNACE-DRAFT FOR BATTERIES OF STEAM-BOILERS.

SPBCIFICATIQN forming part of Letters Patent No. 382,490, dated May 8, 1888.

Applicaion filed January 10, 1858.

Serial No. 260.315. (No model.)

boiler furnaces according to the rate of com-' bustion required in order to maintain a given pressure of steam; and the object of the invention is to so apportion the total a-mou'nt'of air supplied to the furnaces of a whole battery of boilers that the several fires shall be soonest equalized by delivering to each the different amounts of air which their different conditions may require, such equalization being intended for the purpose of increasing the efficiency of the steam regulation under violent fluctuations in the amount of power consumed. This equalization is effected by employing a double system of draft regulation, the total air-supply being regulated by the steam-pressure, the ap portioning of the total to each furnace beingregulated by the temperature of the escaping gases of the same respectively.

In the accompanying drawings a battery of three boilers is represented in diagram, the

form chosen, for clearness of illustration, being of the locomotivetype, although the inven-- tion is obviously applicable to all forms.

Figure 1. is aplan view; Fig. 2, a sectional elevation of the system, taken on the line 00 ac; and Fig. 3, a similar view taken on the line 3 y. A is the common flue, through which the draft is conveyed from the several boilers B G D composing the battery.

E is the air-pipe employed for conducting the air beneath the grates at a, Fig. 2. The features of the invention are applicable to either a forced blast or a natural draft, and the draft-controlling apparatus shown is ap plicable to both methods.

F is the common drum or steamconductor connecting and leading from the several boilers to the point of steam eduction.

b is the main damper, which governs the total amount of air supplied to the whole battery of boilers, the said damper being con= trolled by the action of the varying steamfluid within the bulbs g, exposed to the term 65,

peratu're of the escaping gases from each furnace independently.

. The pipe E may be employed for conducting either a forced or a natural draft. The dampers d and dampers e serve identical functions whether the draft be forced or natural, and

said double sets of dampers d and 6 may be used singly or together, the different-arrange ments being exemplified, as will be under stood by an inspection ofFigs. 2 and 3.

In the operation of the invention the steampressure actuates the main damper I), controlling the general air supply, closing it partially when the pressure rises to the desired point and opening it when the pressu're falls, the 8o consequent amount of air passing throughlthe. grates bearing a definite relation to the amount.

' of coal burned to develop the required horsepower. The amount of coal burned is thus decreased or increased, and the steam generated automatically holdsthe pressure approximately to the desired point under varying demands for steam but the efficiency. of a general draft-control system in which the regulation is extended only to the total air-supplyas applied to a battery of boilers is limited, especially in cases where the amount of power required fluctuates 'very violently, inasmuch as the different conditions of the various fires may require specific amounts of air-supply to control them with quick response.

For illustration, given a battery of three boilers having their fires at different conditions or periods of activity, the fire which has reached the best condition will, receiving the full supply of air, be rapidly forced and comparatively soon'burned out, while contributing the greatest amount of heat. ,The furnace be developing the least share of heat, and, while supplied with the same amount of air as the one previously described, will take some time to reach an equal condition, whereas the third furnace, having its fire nearly burned out, would not receive a greater proportion of air than its condition required. To compensate for these varying conditions, the auxiliary dampers d and dampers e, or both in conjunction, are operated by the fluctuations in temperatures of the fires by means of the thermostats 9 and flexible diaphragms of the regu- 1 formity of combustion promoted throughout the several fires.

The apparatus herein described for practicing the method claimed forms the subject matter of a separate application filed by me June 23, 1887, Serial No. 242, 209.

Having thus fully described my invention, what I claim, and desire to secure by Letters Patent, is-

The method described of first controlling the total air-Supply to the furnaces of a battery of steain boilers by a regulator operated by the varying steam pressure within said boilers, and, second, apportioning said air-supply to the several furnaces by regulators operated by the respective varying temperatures of said furnaces.

NAT. W. PRATT. 

